Semiconductor device package with integrated heat spreader

ABSTRACT

A multi chip housing has a lead frame to which plural die are soldered. A heat spreader conductive cap encloses a volume containing the plural die or chips and is fixed to the periphery of the lead frame. The tops of the die are closely spaced from the interior of the cap and the volume is filled with a thermally conductive, electrically insulating plastic encapsulant.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/732,626, filed Nov. 2, 2005, the entire disclosure of which isincorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to semiconductor devices and more specificallyrelates to a novel package for plural chips or die with improved coolingof the chip or die.

BACKGROUND OF THE INVENTION

Packages for 2 or more semiconductor die are well known. Thus it isdesirable to provide packages with two or more interconnected MOSFETs asfor a buck converter circuit or a general half bridge circuit, or toprovide one or more MOSFETs, or IGBTs or the like with an IC controllerchip in the same package.

The cooling of such packages is a critical problem. It would bedesirable to cool the die in such packages from both surfaces, whilealso permitting economical manufacture and assembly of such packages.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with the invention, a heat spreader clip is integratedinto the multichip package to allow for dual sided cooling forsemiconductor die carried on a lead frame. The clip is soldered orotherwise secured to the lead frame and the volume between the leadframe and clip is filled with a thermally conductive, electricallyinsulative encapsulant. The surface of the clip is closely spaced fromthe die but is electrically insulated therefrom. The novel structurepermits simple, well known, low cost assembly techniques. If desired,passive components such as capacitors, resistors and inductors can bemounted within the enclosed package.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a lead frame used in connection with thepackage of the invention.

FIG. 2 is a cross-section of FIG. 1 taken across section line 2-2 inFIG. 1.

FIG. 3 is a side view of a typical die with solder bump electrodes whichcan be mounted with other such die in the package of the invention.

FIG. 4 is a plan view of the die of FIG. 3 as seen from section line 4-4in FIG. 3.

FIG. 5 shows the mounting of two die which may be of the type shown inFIGS. 3 and 4 on the lead frame of FIGS. 1 and 2.

FIG. 6 shows the mounting of a conductive clip on the structure of FIG.5.

FIG. 7 is a top view of the structure of FIG. 6.

FIG. 8 shows the structure of FIG. 7 after injection of an encapsulantin the volume between the lead frame and conductive clip.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 show a conductive lead frame 20 of conventional materialand which may be stamped or etched as shown. Thus, elongated windows 21,22, 23, 24, 25, 26, 27 are etched or stamped as shown leaving conductivewebs between laterally adjacent windows. Any desired number of windowsof any desired shape can be used.

FIGS. 3 and 4 show a typical semiconductor die 30 which can be mountedwith similar or diverse die in the package of the invention. Die 30 can,for example, be a power MOSFET of any thickness, for example, 50microns, with conventional solder bump contacts which may have a highlead content or could be of an SAC alloy. The bump material can be ofany desired choice. Any desired pattern can be used, governed by thegeometry of the webs between windows 21 through 27 in lead frame 20.

While bump contacts are shown, it will be understood that any othercontact structure and placement can be employed without departing fromthe invention and, for example, planar solderable electrodes can beused. Further, the invention is not limited to use with MOSFETs. Otherdie, including IGBTs, control integrated circuits and the like may becontained, in various combinations, in the novel package of theinvention.

FIG. 5 shows 2 MOSFETs 30 of the type shown in FIGS. 3 and 4 soldered tothe webs of the lead frame 20 by any well known process. Note again thatother semiconductor die can be used in place of one or both of MOSFETs30 or in addition thereto by securement to additional lead frame webs orto webs of greater width than that shown so that 2 or more die can belocated side by side and interconnected by the conductive web to formsome desired circuit connection.

After the die are mounted on the lead frame, and as shown in FIG. 6, aconductive clip or cap 50 is fixed to the lead frame 20. Clip 50 may beof copper and has a flat web portion 51 and a surrounding rim 52. Thebase of rim 52 may be soldered to the periphery of lead frame 20, as bysolder bead 53. Cap 50 has openings 60, 61, 62 which allow subsequentinjection of an electrical insulation encapsulant in the cavity 70formed between cap 50 and lead frame 20. Cap 50 is very closely spacedfrom the top of die 30 and defines a heat spreader for heat generated bydie 30 when the die are energized. By way of example the gap between thebottom of cap 50 and the tops of die 30 may be about 50 microns, butmust be large enough to permit flow of insulation plastic into the gapduring encapsulation.

The volume 70 is filled through openings 60, 61, 62 with a suitablethermally conductive but electrically insulative plastic encapsulant 80,as shown in FIG. 8. The lead frame 20 may then be trimmed at trim lines90 and 91 (FIG. 7). If desired, the web portions may project away fromthe sides of the package to provide pin connections to the package.Alternatively, the package can be surface mounted by contact from thelead frame web to a suitable circuit board.

In the final package, improved two sided cooling is provided for all dieby the lead frame 20 on one side and heat spreader 50 on the other side.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent, to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein.

1. A semiconductor device package comprising: a lead frame having aplurality of spaced contact areas; at least a first and secondsemiconductor die coplanar with one another and each having at least onecontact on one surface thereof, said contact of each of said die beingelectrically and mechanically connected to a respective one of saidplurality of spaced contact areas of said lead frame, the tops of saidfirst and second die being at least approximately coplanar; and aconductive heat spreader fixed to a peripheral area of said lead frameand forming a volume atop said lead frame, which volume contains said atleast first and second die, the interior surface of said conductive heatspreader being parallel to said tops of said first and second die andbeing closely spaced apart from said tops of said first and second dieby a gap of said volume, but insulated from said first and second dieand permitting effective heat transfer from the die to the heatspreader; said conductive heat spreader including one or more openingsallowing access to an entirety of said volume; and said lead frame andsaid conductive heat spreader providing two sided cooling for said atleast first and second die.
 2. The package of claim 1, which furtherincludes a thermally conductive, electrically insulating plastic volumefilling said volume.
 3. The package of claim 2, wherein said conductiveheat spreader has a plurality of openings therethrough for permittingthe injection of said plastic into said volume after said heat spreaderis fixed to said lead frame.
 4. The package of claim 1, wherein at leastone of said die is a MOSFET.
 5. The package of claim 1, wherein at leastone of said die is an integrated circuit and wherein another of said dieis a MOSgated device to be controlled by said integrated circuit.
 6. Thepackage of claim 1, wherein said conductive heat spreader has a capshape with a central web having a rim extending therefrom; said rimconnected to said lead frame.
 7. The package of claim 4, which furtherincludes a thermally conductive, electrically insulating plastic fillingsaid volume.
 8. The package of claim 5, which further includes athermally conductive, electrically insulating plastic filling saidvolume.
 9. The package of claim 6, which further includes a thermallyconductive, electrically insulating plastic filling said volume.
 10. Thepackage of claim 7, wherein said conductive heat spreader has aplurality of openings therethrough for permitting the injection of saidplastic into said volume after said heat spreader is fixed to said leadframe.
 11. The package of claim 8, wherein said conductive heat spreaderhas a plurality of openings therethrough for permitting the injection ofsaid plastic into said volume after said heat spreader is fixed to saidlead frame.
 12. The package of claim 9, wherein said conductive heatspreader has a plurality of openings therethrough for permitting theinjection of said plastic into said volume after said heat spreader isfixed to said lead frame.
 13. A semiconductor device package comprising:a lead frame having a plurality of spaced contact areas; at least afirst and second semiconductor die coplanar with one another and eachhaving at least one contact on one surface thereof, said contact of eachof said die being electrically and mechanically connected to arespective one of said plurality of spaced contact areas of said leadframe, the tops of said first and second die being approximatelycoplanar; a conductive heat spreader fixed to a peripheral area of saidlead frame and forming a volume atop said lead frame, which volumecontains said at least first and second die, the interior surface ofsaid conductive heat spreader being parallel to said tops of said firstand second die and being closely spaced apart from said tops of saidfirst and second die by a gap of said volume, but insulated from saidfirst and second die and permitting effective heat transfer from the dieto the heat spreader; said conductive heat spreader including one ormore openings allowing access to an entirety of said volume; and athermally conductive but electrically insulating plastic encapsulantsubstantially filling said entirety of said volume; said lead frame andsaid conductive heat spreader providing two sided cooling for said atleast first and second die.
 14. The package of claim 13, wherein saidconductive heat spreader has a plurality of openings therethrough forpermitting the injection of said plastic into said volume after saidheat spreader is fixed to said lead frame.
 15. The package of claim 13,wherein at least one of said die is a MOSFET.
 16. The package of claim13, wherein at least one of said die is an integrated circuit andwherein another of said die is a MOSgated device to be controlled bysaid integrated circuit.
 17. The package of claim 13, wherein saidconductive heat spreader has a cap shape with a central web having a rimextending therefrom; said rim connected to said lead frame.
 18. Thepackage of claim 13, wherein said lead frame is configured to form asurface mount for said semiconductor device package.
 19. The package ofclaim 13, wherein said lead frame is configured to form pin connectionsfor said semiconductor device package.
 20. The package of claim 13,wherein at least one of said contact of said die is a planar solderableelectrode.